The expansion of an underground mine (e.g. a coal mine) requires digging a tunnel which initially has an unsupported roof. To stabilize and support the roof, roof bolts must be inserted into the roof to provide support. The operator must first drill holes in the roof through the use of a cutting bit (or roof drill bit) which connects, either directly or by way of a chuck, to a driven drill steel. U.S. Pat. No. 5,400,861 to Sheirer, which is hereby incorporated by reference herein, discloses various roof drill bits and ways to connect the cutting bit to the chuck. See also "Kennametal Mining Products" Catalog A96-55(15) H6 (September 1996) 36 pages!, and "Kennametal Mining Products" Catalog B92-75R(3)M5 (1992) 36 pages!, which are hereby incorporated by reference herein.
After drilling the hole, the operator must remove the cutting bit-chuck-drill steel assembly from the hole prior to inserting the roof bolt. Sometimes during such removal, the cutting bit sticks in the hole so that continued removal results in the cutting bit becoming detached from the balance of the assembly (i.e., the chuck and the drill steel) and remaining in the hole. This is an undesirable happening which necessitates additional effort to extract the cutting bit from the hole.
Heretofore, there have been arrangements to connect the cutting bit to the chuck (or drill steel) with separate mechanical connectors (e.g., pins and clips). These earlier arrangements have experienced some drawbacks.
In order to assembly the cutting bit to the chuck, the operator had to align apertures in the chuck and the cutting bit and then position the connector (e.g., a pin) so as to engage these apertures. The use of this type of assembly to connect the cutting bit to the chuck was time-consuming if the operator had difficulty aligning the apertures. If one or both apertures had debris therein the operator experienced difficulty in passing the connector through (or into) the apertures.
These earlier mechanical connectors were exposed to the mine environment so that they were subject to damage during the drilling operation. In the event of damage to the connector, the connector sometimes did not retain the cutting bit to the balance of the assembly upon removal from the hole thereby leaving the cutting bit in the hole. Damage of the connector sometimes resulted in the operator experiencing difficulty in disassembling the cutting bit from the chuck after removal from the hole.
It thus becomes apparent that it would be desirable to provide a cutting bit-chuck assembly wherein the cutting bit would easily connect or disconnect from the chuck, preferably by hand, and yet, the connection therebetween would be sufficiently strong so as to successfully resist disconnection during removal of the cutting bit-chuck-drill steel assembly from the hole. Furthermore, it would be desirable to provide a cutting bit-chuck assembly wherein the connection between the cutting bit and the chuck would not be exposed to the mine environment so as to reduce the potential for damage thereto.
The drawbacks expressed above with respect to the connection between the cutting bit and the chuck also may exist in the chuck-drill steel assembly and the drill steel-drill steel assembly. Thus, it would be desirable to provide a chuck-drill steel assembly and a drill steel-drill steel assembly which have the above advantages as expressed above for the cutting bit-chuck assembly.